I. Field of the Invention
This invention relates to the controlled oxidation of natural gas to produce primarily methanol with little or no formaldehyde.
II. Description of the Prior Art
Reserves of natural gas in Canada and often in other hydrocarbon-producing countries are quite high although direct utilization of the gas as a power source is inconvenient for reasons of storage, handling and application. Conversion to a liquid fuel would obviate the problems of storage and handling. The most suitable liquid fuel obtainable from natural gas (or more generally from methane which is the main component of natural gas) is methanol which can be used as a direct substitute for gasoline. This conversion can be achieved by the controlled oxidation of methane to methanol, i.e. oxidation under conditions such that further oxidation to higher oxidation state products is limited.
The conventional procedure for the conversion of natural gas to methanol first of all involves a reaction with water to produce synthesis gas, which is a mixture of carbon monoxide and hydrogen, followed by catalytic conversion of the synthesis gas to methanol or other substances.
Since both reactions, i.e. the conversion of natural gas to synthesis gas and the subsequent conversion of synthesis gas to methanol require the presence of a catalyst, high purity gases must be employed and large plants must be constructed in order to achieve an economy of scale. Poisoning of the catalysts invariable occurs and the catalysts must often be replaced or regenerated.
The direct conversion of methane or natural gas to methanol has been attempted in the past, but the conversion yields have not been very high and selectivity for methanol has been low. Moreover, catalysts are also generally employed for such reactions, leading to the problems outlined above. For example, E. H. Boomer in Canadian Patent No. 291,411 issued on Jul. 16, 1929 stressed the need for a variety of catalysts to effect the reaction.
Bone and Newitt in Canadian Patent No. 394,823 issued on Feb. 25, 1941 describe a partial oxidation of gaseous hydrocarbons, but a high proportion of the product is formaldehyde as well as some methanol. Catalysts were also suggested for this reaction.
More recently, Brockhaus and Franke in Canadian Patent No. 1,096,884 issued on Mar. 3, 1981 have described a method of converting methane to methanol and formaldehyde using a flame reactor. The system gives very poor yields and ratios of methanol to formaldehyde which vary from 1 to 4:1, which is quite low.
Accordingly, an object of the invention is to provide a process for the direct conversion of natural gas to methanol which is relatively easy to operate and gives a good yield of methanol with high selectivity.
Another object of the invention is to provide an apparatus for carrying out the above process.